mini_magick debug trace https://arika.org/2017/12/09/create-image-by-minimagick/

mini_magick_debug.rb

require 'shellwords'

class MiniMagickCommandExecutionTrace
  OUTPUT = $stderr
  TERM = {
    green: "\e[32m",
    red: "\e[31m",
    yellow: "\e[33m",
    reset: "\e[m",
  }.freeze

  def initialize
    @tps = [
      TracePoint.new(:call, &trace_call),
      TracePoint.new(:return, &trace_return),
      TracePoint.new(:raise, &trace_raise),
    ]
    @in_trace = 0
  end

  def on
    @tps.each(&:enable)
  end

  def off
    @tps.each(&:disable)
  end

  private

  def trace_call
    lambda do |tp|
      break unless trace_needed?(tp)

      method_id = tp.method_id
      command = tp.binding.local_variable_get(:command)
      puts "=== #{method_id} ================= command (#{Time.now.iso8601})", color: :green
      puts command.shelljoin

      @in_trace += 1
    end
  end

  def trace_return
    lambda do |tp|
      break unless trace_needed?(tp)
      @in_trace -= 1

      timestamp = Time.now.iso8601
      method_id = tp.method_id
      stdout, stderr, status = tp.return_value

      unless stdout.nil? || stdout.empty?
        puts "--- #{method_id} ----------------- stdout", color: :green
        puts stdout
      end

      unless stderr.nil? || stderr.empty?
        puts "--- #{method_id} ----------------- stderr", color: :yellow
        puts stderr
      end

      color = if status.nil?
                :red
              elsif status.respond_to?(:success?)
                status.success? ? :green : :yellow
              else
                status.zero? ? :green : :yellow
              end

      unless status.nil?
        puts "--- #{method_id} ----------------- status", color: color
        puts status.inspect
      end

      puts "=== #{method_id} ================= finish (#{timestamp})", color: color

      puts
    end
  end

  def trace_raise
    lambda do |tp|
      break if @in_trace == 0

      timestamp = Time.now.iso8601
      method_id = tp.method_id
      exception = tp.raised_exception

      puts "--- #{method_id} ----------------- exception (#{timestamp})", color: :red
      puts "#{exception} (#{exception.class})"
      exception.backtrace.each {|l| puts "\t#{l}" }
    end
  end

  def trace_needed?(tp)
    return false unless tp.self.is_a?(MiniMagick::Shell)
    return false unless tp.method_id == :execute_open3 || tp.method_id == :execute_posix_spawn
    true
  end

  def puts(str = '', color: nil)
    if color = TERM[color]
      str = "#{color}#{str}#{TERM[:reset]}"
    end

    OUTPUT.puts(str)
  end
end

mini_magic_trace = MiniMagickCommandExecutionTrace.new
define_method(:mini_magick_debug_on) { mini_magic_trace.on }
define_method(:mini_magick_debug_off) { mini_magic_trace.off }
def mini_magick_debug
  mini_magick_debug_on
  yield
ensure
  mini_magick_debug_off
end

test.rb

#gem 'mini_magick', '=4.2.4'
require 'mini_magick'
require_relative 'mini_magick_debug'

if MiniMagick.logger.respond_to?(:level=)
  MiniMagick.logger.level = Logger::DEBUG
else
  MiniMagick.debug = true
end

Process.setrlimit(:CPU, 1, 1)

mini_magick_debug_on

MiniMagick::Tool::Convert.new do |c|
  c.size '4096x4096'
  c << 'tile:logo:'
  c << '-font' << 'VL-PGothic-Regular'
  c << '-fill' << '#000000'
  c << '-pointsize' << '14'
  c << '-gravity' << 'North-West'
  c << '-annotate' << '+10+10' << 'hoge ほげ'
  c << 'test.png'
end